Sheet transfer mechanism



March 1, 1960 J. K. JANTZEN SHEET TRANSFER MECHANISM 2 Sheets-$heet 1Filed March 1'7, 1959 INVENTOR. JOHA'NNES K. JANTZEN ATTORNEYS ,March 1,1960 J. K. JANTZEN SHEET TRANSFER MECHANISM Filed March 17, 1959 2Sheets-Sheet 2 INVENTOR.

JOHANNES K. JANTZEN ATTORNEYS United States Patent i SHEET TRANSFERMECHANISM Johannes K. Jantzen, Woodland Hills, Calif., assignor toMiehle-Goss-Dexter, Incorporated, Chicago, 111., a corporation ofDelaware Application March 17, 1959, Serial No. 799,879

9 Claims. (Cl. 271-51) This invention pertains to mechanisms for feedingsheets to a printing press or the like machine. More specifically, it isdirected to an improved stop gripper mechanism for transferring sheetsfrom a position at rest on a feed table to the grippers of acontinuously rotating impression cylinder.

It is common practice in the printing industry to feed sheets to a sheetfed printing press by means of an automatically operated, oscillatingsheet transfer or stop gripper mechanism which is provided with gripperfingers and coacting pads to engage and transfer successive sheets froma position at rest on the feed table of the press to the grippers of thecontinuously rotating impression cylinder. On the feed stroke of thecycle, the transfer grippers and pads swing in an are substantiallytangent to the feed table and to the periphery of the impressioncylinder at the transfer point so that each sheet is transferred inregister to the impression cylinder grippers. During the return stroke,the grippers and pads preferably are Withdrawn or retracted within theradius of their normal path of travel so as to preclude interferencewith .and possible damage to the trailing portion of the transferredsheet which is still being withdrawn as the transfer grippers return toengage the leading edge of the next sheet. i

Heretofore control of the transfer gripper fingers and pads has beeneffected by means of rotating cams provided at each end of the mechanismwhich are effective to move the pads between their operative andwithdrawn positions and to control the opening and closing action of thegripper fingers at predetermined intervals to engage and release thesheets. In combination with the cams,.relatively large compressionspring assemblies are provided to maintain the respective cam rollersagainst their actuating cams and to effect the return movements of thegrippers and pads and these assemblies are mounted for bodily movementwith the grippers and pads, as illustrated for example in Patent1,790,457. In most instances a corresponding spring assembly is providedat each end of the mechanism to control the movement of the gripper padsand an a dditional spring assembly is provided, usually at one end onlyof the device, to effect the closing action of the gripper fingers.

These external spring assemblies, not only require considerable space ina relatively confined area of the printing press, but the mass of therespective elements associated therewith, such as the supportingbrackets, the sliding pins, and the springs themselves, adds materiallyto the total inertia which must be accelerated, retarded, and reversed;rapidly during each cycle of operation. Consequently,;it has beennecessary to employ relatively heavy structural members to withstand thestresses imposed thereon and the ability to maintain positive control ofsuch a heavy unit has constituted a limiting factor in determining themaximum speed at which the mechanism can safely be operated. Moreover,because of the rather extensive movement imparted to the grippers andpads and the resultant constant flexing of the springs, they 2,926,909Patented Mar. 1, 1960 are relatively short lived and must be replaced atfrequent intervals.

It is an object of this invention, therefore, to provide a transfermechanism of improved design which is considerably lighter in weight,more efficient in operation and which will permit higher operatingspeeds.

A further object is to provide a transfer mechanism wherein the multipleexternal compression spring assemblies are eliminated and the forcenecessary to maintain the respective actuating members in contact withtheir control cams is provided by a single, fully enclosed, resilientspring member.

Another object is to provide a sheet transfer mechanism wherein thetension of the resilient spring member is maintained substantiallyconstant during the complete cycle of operation.

A still further object is to provide adjustable means for preloading theresilient member and whereby the tension at each end thereof can beequalized.

Other objects and advantages of this invention will be apparent from thefollowing description and the accompanying drawings wherein:

Figure 1 is a view, partly in section showing the improved transfermechanism in its sheet engaging position with respect to the registertable;

Figure 2 is a view similar to Figure 1 showing the position of therespective elements immediately after passing the sheet transfer pointwith respect to the impression cylinder;

Figure 3 is a plan view, partly in section, taken substantially alongthe line III-III of Figure 1; and

Figure 4 shows the mechanism for preloading and equalizing the tensionon the torsion bar.

With reference now to the drawings the sheet transfer mechanism in whichthe invention is embodied for purposes of illustration comprises a mainsupporting shaft 10, having gripper fingers 11, and coacting pads 12mounted thereon for transferring sheets from a register position againstthe front guides 13 on. the feed table 14 to the grippers 16 on theimpression cylinder 17.

The shaft 10 is journaled for rotation about an axis parallel with theimpression cylinder and above the leading edge of the feed table and isadapted to be oscillated in timed relation with the rotary motion of theimpression cylinder so that a sheet will be presented to the impressioncylinder grippers for each revolution of said cylinder. The mechanismfor oscillating the shaft has not been shown because it forms no part ofthe present invention and any well known mechanism, such as thatdisclosed in Patent 1,764,104, may be used for the purpose. It will beunderstood, however, that the motion of the shaft is such that thetransfer grippers, after they have engaged a sheet at rest on the feedtable, will be gradually accelerated until they are traveling at thesame speed as the impression cylinder when they reach the transfer pointand release the sheet to the impression cylinder grippers.

As shown in Figures 1 and 2, the gripper fingers 11 and pads 12 aremounted on the shaft 10 by means of brackets 18, a series of which arefixed to said shaft in spaced relation and which project radiallytherefrom to provide support for a gripper shaft 19. The latter isrotatably mounted in the brackets and provides support for the gripperfingers 11 a series of which are clamped securely to said shaft so thatthey will move in unison therewith when the shaft is oscillated for thepurpose of opening and closing the grippers at predetermined positionsin the cycle of operation.

Rocking motion of the gripper shaft 19 about its axis in the brackets 18is effected by means of a cam 21 which is mounted for rotation about theaxis of the supporting shaft journal 22 and engages a cam roller 23 onthe lever 24 which is secured to the end of the gripper shaft,

The cam 21 is mounted for rotation in a counter clockwise direction asviewed in Figures 1 and 2 and as said cam rotates, the gripper shaftwill be rocked intermittently whereby to open and close the gripperfingers at predetermined intervals during the cycle of operation. Themechanism for driving the cam has not'been shown, but it will beunderstood that it is driven preferably at afconstant rate-of speed, byany suitable means such as for example by the cylinder driving gear, soas to make one complete revolution for each cycle of operation.

Whereas the gripper fingers 11 are fixed to the gripper shaft 19 so asto move in unison therewith, the coacting gripper pads 12 are mountedfor relative oscillating motion about the axis of the gripper shaft, sothey can be rocked between their operative and retracted positionsduring their respective feed and return strokes. Accordingly the padsare fixed to a T-shaped supporting bar 26 which extends transverselyacross the feed table parallel to the gripper shaft and which is mountedby means such as the bolts 27 to the respective ends of a series oflevers 28and 29 which are rotatably mounted on the gripper shaft.

During the feed and return strokes of the transfer cycle the angularposition of the gripper pads is controlled by a cam 30 which is mountedto rotate with the gripper finger control cam 21 through one completerevolution for each cycle of operation and which actuates a cam roller31 on the lever 32, see Figire 3, which is formed integral with thegripper pad supporting levers 28, one of which is provided at each endof the gripper pad assembly.

From the description thus far it will be evident that when the shaft isoscillated, the gripper fingers 11 and pads 12 will swing back and forthbetween the feed table and the impression cylinder and the cam 21, whichrotates constantly in the direction indicated by the arrows in Figures 1and 2, will open and closethe gripper fingers atpredetermined intervalsto engage a sheet on the feed table and to release it to the impressioncylinder grippers at the transfer point. In a similar manner, the cam 30will maintain the gripper pads 12 at a radius coincident with the normalplane of transfer, indicated by the broken line A-A in Figures 1 and 2,until they have passed the transfer point and have reached the end ofthe feed stroke which position is indicated by broken lines in Figure 1.At this point the cam 30 is effective to retract or withdraw the padsand therewith the gripper fingers within their normal radius of travelas the direction of movement of the shaft 10 is reversed and thegrippers and pads return to engage the next succeeding sheet.

The force required to maintain the cam follower rollers 23 and 31 incontact with their respective cams is provided by a single, resilientspring member in the form of a torsion bar 33 which is mounted coaxiallywithin the hollow gripper shaft 19. As shown best in Figure 3, thegripper shaft is formed with a reduced diameter neck portion 34substantially at the center thereof'which is provided with grooves toreceive the enlarged splined portion 36 of the torsion bar. In this waythe two members are locked securely together so that any rotary motionof the gripper shaft will be transmitted to the torsion bar at thispoint. At its outer ends, however, the torsion bar is arranged to rotaterelative to the gripper shaft and each end is formed with an enlargedbearing portion 37 which is rotatably mounted in a bearing 38 insertedinto each end of the gripper shaft.

In order to transmit the force of the torsion bar to the gripper padcontrol levers 32, which are rotatably mounted on the gripper shaft,each end of the torsion bar which extend beyond the ends of the grippershaft is provided with a lever 39. These levers have internally groovedopenings to fit securely onto the splined end of the torsion bar andthey are clamped in position by means such as the bolts 41. The free endof each lever 39' extends laterally from the torsion bar, as shown inFigure 4, and engages an eccentric pin 42 formed integral with therespective cam roller studs 43 which are carried at the free ends of thelevers 32 and support the cam rollers 31. Thus it will be evident thatthe torsion bar is connected between the respective cam levers and willexert a constant, equalized force against each one to maintain the camfollowers against their respective control cams.

At assembly the levers 39 are aflixed to the torsion bar at an angularposition which is such that when the.

cam rollers 23 and 31 are placedin operative position on theirrespective cam surfaces, the torsion bar will be placed under apredetermined preload tension. For efficient operation this tension mustbe sufiicient to overcome the forces exerted against the respective camlevers and it must be substantially equal at each end of the assembly.

After the initial preload tension has been imposed on the torsion bar byappropriate positioning of the levers 39, any differential in thetension at each end thereof can be corrected by varying the angularposition of the pins 42. As shown in Figures 3 and 4 the pins are formedintegral with the studs 43 and these are secured to the levers 32 bymeans of locking nuts 44. By loosening the locking nuts the pinsmay beadjusted angularly about the axis of thestuds 43 to thereby increase orrelieve the tension at the respective ends of the torsion bar until itis precisely equal to each end of the assembly.

Obviously the gripper shaft 19 andtorsion bar 33 may eachbe of one piececonstruction so that each extends across the full width of the devicewith the torsion bar being connected to the gripper shaft at its centerportion as heretofore explained. However, for convenience of assemblyand subsequent servicing the gripper shaft preferably is formed of twoseparate sections which are coaxially aligned. In such case the innerend of each section is provided with splines which fit into a coupling45 which locks the two sections together against any relative motion.The torsion bar likewise may be composed of two separate sections which,as shown in Figure 3, are adapted to butt together at the center of thegripper shaft and thus each section, in effect, controls its respectivehalf of the transfer gripper assembly.

In orderto maintain the register position of the sheet as it is beingtransferred, the transfer gripper assembly must be maintained relativelyrigid and in precise alignment from the moment that the transfergrippers close on'a sheet on the feed table and until it is released tothe impression cylinder grippers at the transfer point. To insureaccurate alignment and positioning of the gripper pads during thiscritical portion of the transfer cycle, the clockwise movement of thepad. assembly about the axis. of the gripper shaft 19 is limited by aseries of stops 49, see Figures 1 and 2, which are provided at spacedintervals across the full length. of the transfer mechanism. These stopsare carried at the free ends of the arms 48'formed integral with thecenter pad bar supporting levers 29 and'are arrangel to engage coactingfixed stops 51 provided on the brackets 18. Corresponding stops are alsoprovided on the arms 32 of the levers 28 as shown in Figure3.

By appropriate adjustment of the stops 49 when the pads are in the sheettransfer position, as shown in Figure 1, the pad supporting bar 26 canbe accurately alined throughout its full length to preclude anydistortion or twist therein which would adversely affect-the register ofthe sheet. The stops are preferably set so that the pad cam roller 31 ismaintained slightly spaced from the cam 30 during the sheet transferportion of the cycle during which time the force exerted by the torsionbar maintains the respective stops in intimate contact and the registerof the sheet is precisely maintained. The stops 49 also serve toposition the pads 12 radially, relative tothe feed table and theimpression cylinder, so that they swing in an are having a radiustangent respect to its journals 22. This is done in order to counterbalance the mass of the gripper finger and pad assembly and to avoid theneed for adding counter balancing means which otherwise would benecessary and which obviously would increase the overall weight of themechanism and thus add to the inertia which must be controlledefiiciently at high speeds.

Having thus described the various elements of the invention a briefdescription of its operation is as follows:

As illustrated in Figure .1 the gripper fingers and coacting pads haveengaged a sheet on the feed table in a register position against thefront guides 13. In this position the gripper pad cam roller 31 is onthe low portion 53 of its cam 30 and the gripper finger cam roller 23 ison the low part 54 of its cam 21.

At this point the guides 13 swing down out of the path of the sheet asindicated in Figure 2 and the shaft is rocked in a clockwise directionto swing the trans fer grippers in a circular path indicated by thebroken line AA from the feed table to the impression cylinder.

The movement of the shaft 10 is such that the transfer grippers arerapidly accelerated until they are traveling at the same speed as theimpression cylinder when they reach the transfer point as illustrated inFigure 2. At this point the high portion 56 of cam 21, which is rotatingconstantly in a counter clockwise direction, will engage the gripper camroller 23 thereby rocking the gripper shaft 19 to open the gripperfingers and release the sheet to the impression cylinder grippers. Itwill be noted that during the travel from the feed table to the transferpoint the gripper pad cam roller 31 traverses a concentric portion ofthe cam 30 so that the pads remain precisely in the plane of transferwith the adjustable stops 49 in intimate contact with the fixed stops51.

After the sheet is released to the impression cylinder grippers at thetransfer point, the transfer gripper assemoly continues to mov e in aclockwise direction, but at a decelerating rate, until it reaches theposition indicated by the broken lines in Figure 1. At this point thegripper finger cam roller 23 engages the low portion 57 of its actuatingcam so that the fingers close on the pads as the latter move to aretracted position within the radius of the normalplane of transfer byvirtue of the pad cam roller 31 engaging the high portion 58 of itscontrol cam 30. a

The direction of movement of the shaft 10 is reversed at this point andthe grippers and pads move counter clockwise in their retracted positionuntil they approach the leading edge of the feed table. During thisportion of the cycle, the gripper assembly moves in the same directionand at substantially the same speed as the control cams 21 and 30 andthus the fingers and pads remain in the retracted position. The gripperassembly decelerates as it. approaches the feed table, however,whereupon the high part 59 of cam 21 engages the roller 23 to open thegripper fingers as the tail end of the transferred sheet clears thefront guides 13. Cam roller 31 subsequently engages the low portion 53of its cam 30 causing the pads 12 to be projected to their sheetengaging position over the leading edge of the feed table. Continuedrotation of cam 21 after the transfer grippers come to rest in theirsheet engaging position causes the high portion 59 to move out fromunder the cam roller 23 thereby permitting the gripper fingers to closeon the next registered sheet and the cycle is then repeated.

It will be noted that during the complete cycle of op eration, thetension on the torsion rod remains substantially constant although thepositions of the gripper fingers and pads are varied substantially. Thisis due to the fact that during the travel between the feed table and theimpression cylinder, the cam rollers engage relatively concentricportions of their respective actuating cams and this condition remainsconstant until the gripper fingers 11 are opened at the transfer point.As the transfer mechanism continues on past the transfer point thegripper finger cam roller moves to a low portion of its actuating cam asthe pad cam roller 31 engages a high portion of its cam to retract thegrippers within the normal path of travel. Thus the tension on thetorsion bar remains substantially constant at this point because theassembly, in effect, merely pivots about the axis of the gripper shaftas a unit with little or no relative motion between the respectivecontrol levers.

On the return stroke also the respective cam rollers maintain relativelyfixed positions until they approach the feed table at which time thegripper fingers are opened as the cam roller 23 engages a high portionof the cam 21 and the gripper pads move substantially in the samedirection as they are projected to their sheet taking position when thepad cam roller 31 moves to a low portion of its actuating cam. Thus itwill be evident that during the complete cycle of operation the fingersand pads pivot substantially as a unit about the axis of the grippershaft and the only substantial relative motion between the respectivecontrol levers takes place at the points where the gripper fingers areopened to engage and release sheets. a

This is a definite advantage because it permits the use of relativelylight Weight elements in the transfer gripper assembly without danger ofimposing excessive strains on the operating members and, moreover,because of the minimum relative motion required, a light weight torsionbar can be employed which in turn can be preloaded to any degreenecessary to insure efiicient and accurate operation without danger ofexceeding its modulus of elasticity.

While we have herein disclosed a torsion bar as the preferred means forsupplying the force necessary to maintain the gripper finger and pad baractuating levers in contact with their respective cams, it will beevident that similar results may be obtained by using suitable coilspring means forthis purpose. Therefore, the invention is not to belimited to specific details because other modifications will beapparentto those skilled in respectively inropposite directions about the axisof said shaft, and a single resilient member connected between saidfingers and pads for exerting a substantially constant, equalizedforceagainst said respective actuating means.

2. In a sheettransfer device for feeding sheets from a support to acontinuously rotating impression cylinder, the combination comprising ahollow shaft mounted for oscillation in an arcuate path between saidsupport and said cylinder, gripper fingers and coacting; pads mountedfor bodily movement with said shaft, actuating means for impartingrelative motion to said fingers and pads respectively, in oppositedirections about the axis of said shaft, and a resilient member mountedcoaxially Within said shaft for exerting a substantially constant,equalized force against said respective actuating means.

3. In a sheet transfer device for feeding sheets from a support to acontinuously rotating impression cylinder the combination comprising, ahollow shaft mounted for oscillation in an arcuate path between saidsupport and said cylinder, gripper fingers and coacting pads.

mounted onsaid shaft for bodily movement therewith, cam means-forimparting relative motion to said fingers and pads respectivelyinopposite directions about the axis of said shaft, a resilient memberconnected between said fingers and pads for exerting a substantiallyconstant, equalized force against said respective cam means, lcver meansforapplying a preload tension to said resilient member, andadjustablemeans having coaction with said lever means for equalizing the tensionat each end of said member.

4. in a sheet transfer device for feeding sheets from a support to acontinuously rotating impression cylinder the combination comprising, arotatable shaft, a series of gripper fingers fixed to said shaft, anassembly of coacting gripper pads rotatably mounted on said shaft, meansfor swinging said shaft and therewith said fingers and pads in anarcuate path between said support and said cylinder, actuating means forrocking said pad assembly about the axis of said shaft whereby towithdraw the pads and therewith the fingers within said arcuate pathduring the return stroke of their oscillating cycle, additionalactuating means for rocking said shaft and there with said fingersrelative to said pads at predetermined intervals to engage and releasesheets, and a single resilient member connected between said shaft andsaid pad assembly for exerting asubstantially constant, equalized forceagainst both said actuating means.

5. In a sheet transfer device for feeding sheets from a support to acontinuously rotating impression cylinder the combination comprising, arotatable hollow shaft, a

' series of gripper fingers fixed to said shaft, an assembly of coactinggripper pads rotatably mounted on said shaft,

means for swinging said shaft and therewith said fingers and pads in anarcuate path between said support and said cylinder, actuating means forrocking said pad as sembly about the axis of said shaft whereby towith-- draw the pads and therewith the fingers within said arcuate pathduring the return stroke of their oscillating cycle, additionalactuating means for rocking said shaft and therewith said fingersrelative to said pads at predetermined intervals to engage and releasesheets, and spring means mounted coaxially within said hollow shaft andconnected between said shaft and said pad assembly for exerting asubstantially constant, equalized force against I path during the returnstroke of their'oscillating cycle,

additional actuating means for rocking said shaft and .therewith saidfingers relative to said pads at predetermined intervals to engage andrelease sheets, and a torsion rod mounted coaxially within said hollowshaft and connected between said shaft and said pad assembly forexerting a, substantially constant, equalized force against bothsaidactuating means.

7. In a sheet transfer device for feeding sheets from a support to acontinuously rotating impression cylinder the combination comprising, arotatable hollow shaft, a series of gripper fingers fixed to saidshaft,an assembly of coacting gripper pads rotatably mounted on said shaft,means for swinging said shaft and therewith said fingers and pads in anarcuate path between said support and saidcylinder, cam actuated meansfor rocking said pad assembly about the axis of said shaft whereby towithdraw the pads and therewith the fingers within said arcuate pathduring the return stroke of their oscillating cycle, additional camactuated means for rocking said shaft and therewith said fingersrelative to said pads at predeter mined intervals to engage and releasesheets, a torsion bar mounted within said hollow shaft, said bar andshaft being interconnected substantially at the centers thereof, a leverfixed to each end of said torsion bar for preloading said bar andtotransmit the force thereof to said pad actuating means, and adjustablestops having coaction with said levers for equalizing: the tension ateach end of said torsion bar.

8. In a sheet transfer device for feeding sheets from a support to acontinuously rotating impression cylinder the combination comprising, asupporting member rotatably mounted parallel to said cylinder, a seriesof brackets fixed to said member, a hollow shaft rotatably mounted insaid brackets, a series of gripper fingers fixed to said shaft, anassembly of coacting gripper pads mounted for rotary motion about theaxis of said shaft, drive means for oscillating said supporting memberwhereby to swing said fingers and pads in an arcuate path between saidsupport and said cylinder, cam actuated means for rocking said padassembly about the axis of said shaft whereby, to retract said pads andfingers within said arcuate path during the returnstroke of theiroscillating cycle, additional cam actuated means for rocking said shaftrelative to said pads whereby to open said gripper fingers atpredetermined intervals, and a resilient member mounted coaxially withinsaid shaft and having a connection between said pads and fingers foreffecting the return movements of both said fingers and said pads.

9. In a device for transferring sheets from a support to a: rotatablesheet carrying member the combination comprising, a shaft mounted formovement between said support and said member, gripper fingers andcoacting pads mounted for bodily movement with said shaft, actuatingmeans for imparting relative motion to said fingers and padsrespectively about the axis of said shaft, and a single resilient memberconnected between said fingers and pads for exerting a substantiallyconstant, equalized force against said respective actuating means.

References Cited in the file of this patent UNITED STATES PATENTS

